AVIATION safety experts have grounded an entire fleet of waterbombing planes as an inquiry continues into the cause of a fatal crash during firefighting operations near Ulladulla.

The Civil Aviation Safety Authority made the decision to allow time to conduct stringent maintenance inspections on all 30 M18 Dromader planes in Australia.

The grounding comes as an ongoing investigation by the Australian Transport Safety Bureau revealed the wing of the M18 Dromader which crashed last month was cracked before take-off.

Father-of-three David Black, 43, died when the aircraft crashed into rugged terain in Budawang National Park as he was waterbombing a bushfire on October 24.

David Black and his wife Julie / Picture: FacebookSource:No Source

CASA, which is conducting its own investigation, released a statement: "The grounding is to allow work to continue on reviewing safety issues relating to maintenance inspections and the operation of the aircraft.

"CASA is obtaining maintenance data and information from the Dromader operators. This will be carefully analysed before Dromader flights resume."

The ATSB said in an update into the crash that a preliminary on-site examination had found a part of the left outer wing had fractured through an area of "pre-existing fatigue cracking".

The stress on the compromised structure from the water-bombing operations resulted in wing separating while in flight, it said.

"The ATSB team examined the joints closely to determine the failure mode that resulted in the in-flight separation of the wing," the report said.

"Preliminary examination indicated that the left outer wing lower attachment lug had fractured through an area of pre-existing fatigue cracking in the lug lower ligament

The aircraft was one of five M18 Dromaders hired by the NSW Rural Fire Service to waterbomb fires.

Helicopters will be operating alone after the grounding of waterbombing planes.Source:News Limited

NSW Rural Fire Service Commissioner Shane Fitzsimmons said the organisation had been using the Polish-designed Dromaders less frequently in recent years, with firefighters favouring the faster Air Tractor AT-802 .

"We have around 100 aircraft that we contract or hire to fight fires, including 27 fixed-wing planes for waterbombing," Mr Fitzsimmons said.

"The grounding will make a difference, but no it is not significant.

"Last month, we only had two Dromaders in action. One of the main reasons we use the Air Tractor is that they are faster."

Mr Fitzsimmons said he supported the grounding of the planes.

"Pending a determination of what caused the aircraft to crash, we support the decision to ground the planes as a sensible one," he said.

"Of the five Dromaders we use, only two have been in operation in the recent fires.

"We have been using the more modern Air Tractor AT-802 planes, which are faster than the Dromaders and cover more ground."

The plane was operated by Rebel Ag in Trangie, and had been contracted to the Rural Fire Service for firefighting.

A witness claimed the aircraft's left wing separated before hitting the tail shortly before the plane crashed.

"The fatigue cracking reduced the structural integrity of the fitting to the point where operational loads produced an overstress fracture of the remaining lug material."

Mr Black was honoured by the NSW Rural Fire Service with a posthumous award for protecting the community.

David Black flying his plane / Picture: FacebookSource:Supplied

LOW BLOW AS THIEVES HIT SCHOOL - Lisa Power and Malcolm Holland

THIEVES have dealt a sickening blow to a Blue Mountains school community, taking advantage of bushfire damage to steal thousands of dollars of vital equipment.

Televisions, 16 computers and canteen supplies worth a total of $30,000 were taken in the Monday night raid on Springwood's St Columba's High School.

The looters damaged windows and even stole the school's emergency advisory computer, which was used to keep worried parents informed while students were kept safe during the October bushfires.

"We used that computer very successfully during the recent fires,'' principal Delma Horan said.

"Our kids don't need to have this sort of treatment at a time when they are still struggling with what they have been through, and the staff and the parents.

"We will get insurance but we are going to have to divert from emergency funds while we wait for that.''

Mrs Horan said the telephone line to the school's alarm system was burnt through during the fires but thieves struck before it could be repaired.

The school has been helping with counselling, fee relief and uniform donations for staff and students who lost homes in the bushfires.

Police investigating the school robbery are also investigating a raid on the fire-ravaged Zig Zag Railway.

Staff and volunteers discovered on Monday morning that looters had taken advantage of damaged fencing to strip the site of thousands of brass screws used to repair and maintain the famous tourist attraction's historic carriages.